As portable devices continue to get smaller, the pressure on device designers to reduce the number of external connectors increases. One popular method of reduction is to use a single connector on the portable device that can perform different operations previously provided by several different traditional connectors, such as power and data transfer on the portable device. Unfortunately, a standard multipurpose connector is often not as fast at a particular operation as a dedicated connector for that same operation.
Additionally, due to increased power/charging demands by consumer devices, the portable device industry has been racing ahead of existing power/charging standards with proprietary non-standard charging methodologies in an attempt to support charging on their devices at higher rates. Thus, while the USB (Universal Serial Bus) standard does allow for power delivery across its connection, the standard current levels provided under the standard are rarely comparable to those of a dedicated charger. For example, a standard USB downstream port (SDP) only supplies a maximum of 500 mA at 5V, which means that charge times using the USB On-The-Go (OTG) standard are substantially longer. As a result device manufacturers continue to proliferate non-standardized and incompatible charging methods, which may result in damage to both the portable device and connected chargers whenever incompatibly matched.
Moreover an OTG compatible portable device may only be able to perform one operation at a time. For example, on certain portable devices, a data transfer operation may preclude a charging operation. More particularly, in some configurations, the standard multipurpose connectors cannot provide simultaneous data transfer and charging of the portable device. This is particularly true when the different operations require the portable device to be configured as two completely different devices. For example, during a data transfer a portable device may be connect to a powered USB Hub, which has no means by the baseline USB standard to charge the attached portable device. More specifically, the USB standard requires that the lone 5V power line of the USB Hub may not allow back-voltage across the connection to the attached portable device. To obtain compliance with the standard, this 5V power line of the USB Hub is typically blocked with a one-way circuit element, such as a diode, which directly interferes with any ability to charge using that 5V power line. Thus, according to the requirements of the USB standard, the portable device cannot be simultaneously connected to both a USB charger and a USB Hub. Moreover, even though the USB charging ports use the same standard Type-A USB connector, dedicated charging ports (DCP) are used strictly for power and require no host connection but offer no data transfer capabilities as a result. Unfortunately, even charging downstream ports (CDP), which support data transfers and can provide up to 1.5 A to connected USB peripheral devices (three times the power available on a standard USB port), do not provide enough current to quickly charge modern high-current and battery-powered portable devices.
Accordingly, because of the previously mentioned limitations of existing USB chargers, each portable device often employs special signaling mechanisms to identify when a connected charger may provide a customized, and often accelerated, charge to the portable device. Unfortunately, these signaling mechanisms are typically non-standardized signals sent using the USB data lines and thus directly interfere with simultaneous data transfer.